This project encompasses all statistical coordinating center responsibilities for collaborative clinical studies undertaken by this Section and the Office of the Chief. A major initiative involves the study of the etiology of Parkinson's disease (PD) using the twin pair registry of the National Academy of Sciences-National Research Council. The prevalent cases of PD in the more than 6,000 twin pairs in which both members are alive, will be identified. This observational study will establish: environmental, medical and family histories of both affected and unaffected members of the twin pairs; DNA banking; and measurement of progression of disease over time. This project will investigate genetic and environmental contributions and their interactions to the etiology of PD. A Cooperative Agreement has been funded for the clinical aspects of this study. BFSB is acting as the statistical coordinating center. A second collaborative project involves a prevalence survey of major neurologic disorders in Junin, Buenos Aires Province, Argentina. This household survey, funded by the Fundacion para la Investigacion Neuroepidemiologica, is one of the largest of its kind in Latin America. More than 20,000 residents of Junin were screened using systematic sampling techniques, and those suspected of having a disorder of interest were examined by project neurologists. BFSB has collaborated on the design and data collection phases of this study, and will collaborate on the data analysis and preparation of manuscripts.